Shaped bodies of lightweight, foamed plastic, such as `styrofoam` are formed by various known methods including molding, extrusion, and the like. The formation of a foamed plastic body of complex exterior shape normally requires a batch molding process, such as injection molding, or a cutting process wherein the shaped body is cut from a relatively large blank or billet. Because molds such as injection molds, rotational molds and the like, require a substantial investment, the molding processes are normally used only when the molded parts are manufactured in extremely large quantities, and when the number of different molded bodies or parts is limited. The cutting process, on the other hand, is more flexible and can be used to produce foamed bodies of varying shapes and sizes.
For example, where individual lots of shaped, foamed plastic bodies are manufactured in response to varying end use specifications; or where numerous large lots of plastic bodies must be supplied to meet many different specifications, the cutting method can allow such production while minimizing capital investment. However cutting processes also generate substantial waste as portions of the workpiece blank or billet are removed to form the shaped body. Although the scrap is discarded, the material cost associated with the scrap increases the ultimate cost of the foamed plastic body.
Because foamed plastic bodies can have easily deformable exterior surfaces, protective packaging is often needed during shipping of the finished foamed articles. In some instances, plastic foam scrap generated during the cutting operation has been used to form a portion of such protective packaging because scrap pieces have a shape complementary to portions of the exterior of the cut article. However this is only practical with relatively simple shapes and when only a small number of cutting steps are used because complex shapes and multi-step cutting processes generate numerous scrap pieces of differing shapes and sizes that cannot readily be put back together.
Recently, foamed plastic bodies have been used with substantial commercial success as forms for the on-site formation and installation of drainage trenches as disclosed in U.S. patent application Ser. No. 07/768,610 entitled "Trench Forming Assembly and Method" of Lannie L. Stegall. In accord with a preferred method disclosed therein, a plurality of elongate foamed plastic bodies of a predetermined shape are aligned in end to end contact within a preformed ditch. A hardenable trench forming composition, such as concrete, is poured around the aligned form bodies. The hardenable composition is allowed to set around the form bodies and thereafter the form bodies are removed to produce a unitary drainage trench having the shape of the form bodies.
In the above-identified method, the foamed plastic form bodies must be cut according to relatively accurate tolerances so that the aligned form bodies will match at their abutting ends. Thus the cross-sectional profile of each individual form body, particularly at its ends, is preferably identical to the profile of the abutting form body.
In many instances, drainage trench specifications require a sloped bottom surface along the length of the trench to facilitate drainage. Accordingly, the foamed plastic bodies used to form the drainage trench must also have correspondingly sloped bottom surfaces. In such cases the profile or cross-section of each form body must be taller at one end and shorter at the other, but the widths must be identical. The end profiles of adjacent, aligned form bodies must also match closely so that the drainage trench will have a relatively continuous sloping bottom surface. This has been achieved in the past typically by manually aligning identical form bodies; marking a continuous cut line of a desired slope along the aligned bodies and then cutting the bottoms of the individual form bodies along the cut mark.
Foamed plastic bodies of predetermined shapes adapted for assembly into larger bodies are also used in numerous other instances throughout commerce, for example to provide artificially sloped surfaces for sporting activities such as artificial pitcher's mounds for baseball; and for other end uses such as sloped surfaces for roofing surfaces on buildings. In these and similar uses, the individual foamed plastic bodies must be precisely shaped so that they can be assembled to form the desired final larger shape. However, when a cutting processes is used to shape the individual bodies, a custom operation is often required. This precision shaping and matching of surfaces can be labor intensive and costly, and as indicated above, often generates large amounts of waste.